BIOTYPES AND HYBRIDS. 41 



were sown June 5, 1906, and produced a uniform progeny of 145 plants, 

 all like the parent. 



0514.131 : This specimen was, like the last, B. bp. tenuis. Purely fer- 

 tilized seeds were sown June 6, 1906, and the 52 plants produced were all 

 alike and like the parent. 



0514.146 : This was of the dominant type, B. bp. heteris. The pollina- 

 tion was probably not guarded, as no note was made regarding- it. The 

 seeds were sown June 20, 1906, and produced 444 offspring belonging to 

 the dominant and recessive forms in the ratio 317 : 127 or 2.5 : 1. The 

 dominant group appeared to belong to two distinct types, with the pri- 

 mary lobes broader and less sharp in the one than in the other in the ratio 

 110 : 32 or 3.44 : 1. The significance of the ratio thus formed by this 

 family, 9 : 3 : 4, is well known, as it represents the simplest modification 

 of the ratio for the second generation of a di-hybrid, but without further 

 data in support of this composition for the family, it appears advisable not 

 to consider its significance at this time. 



0514.161 : This was a typical specimen of the recessive form, B. bp. 

 tenuis, of which the pollination was guarded. The seeds were sown July 

 4, 1906, and produced 104 specimens, all of which were like the parent. 



0514.162 : This was also an extracted recessive. Guarded seeds were 

 sown July 4, 1906, and gave a progeny of 15 specimens, all like the parent. 



0514.164: A member of the dominant group, B. bp. heteris. Purely 

 fertilized seeds sown July 4, 1906, produced 134 plants. The family was 

 badly damaged by aphis, so that 23 were killed and about 15 more so stunted 

 as to make classification uncertain. The remaining 93 belonged to B. bp. 

 heteris and B. bp. tenuis in the ratio 66 : 27 or 2.44 : 1. In this family 

 the dominant group was not scrutinized with sufficient care to determine 

 whether it was heterogeneous like 0514.146, but it was considered of a 

 single type. 



0514.165 : This was a typical specimen of the dominant type, B. bp. 

 heteris. Purely fertilized seeds were sown July 4, 1906, and produced 42 

 specimens of B. bp. heteris and 13 of B. bp. tenuis, the ratio being 3.23 : 1. 



0514.182 : Although the notes are defective regarding the character of 

 this plant, the result of the breeding test leaves no doubt that it was a re- 

 cessive. Guarded and purely fertilized seeds were probably sown in July, 

 1906, though no record can be found to that effect. On August 18, 1906, 

 the entire progeny, consisting of 158 specimens, were potted, and without 

 exception these belonged to B. bp. tenuis. 



These 8 families belonging to the third or later hybrid generation of B. 

 bp. heteris X tenuis represent the extracted recessive in 5 cases and the 

 heterozygous form in 3. The extracted recessives have bred true to the 



